Circuits and methods for processing signals generated by a circular vertical hall (CVH) sensing element in the presence of a multi-pole magnet

ABSTRACT

A magnetic field sensor has a circular vertical Hall (CVH) sensing element with a plurality of vertical Hall elements disposed over a common implant region in a substrate. The plurality of vertical Hall elements is disposed in an x-y plane. The magnetic field sensor is responsive to a magnetic field generated by a multi-pole magnet having a plurality of north poles and also a plurality of south poles arranged in a plane parallel to the x-y plane, and, in some embodiments, arranged in the x-y plane. A corresponding method is also described.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

FIELD OF THE INVENTION

This invention relates generally to electronic circuits, and, moreparticularly, to an electronic circuit having a circular vertical Hall(CVH) sensing element used in the presence of a multi-pole magnet, andthat can provide an improved output signal with a higher angular (orpositional) resolution while taking no additional time to provide theimproved signal.

BACKGROUND OF THE INVENTION

Planar Hall elements and vertical Hall elements are known types ofmagnetic field sensing elements that can be used in magnetic fieldsensors. A planar Hall element tends to be responsive to magnetic fieldperpendicular to a surface of a substrate on which the planar Hallelement is formed. A vertical Hall element tends to be responsive tomagnetic field parallel to a surface of a substrate on which thevertical Hall element is formed.

Other types of magnetic field sensing elements are known. For example, aso-called “circular vertical Hall” (CVH) sensing element, which includesa plurality of vertical magnetic field sensing elements, is known anddescribed in PCT Patent Application No. PCT/EP2008/056517, entitled“Magnetic Field Sensor for Measuring Direction of a Magnetic Field in aPlane,” filed May 28, 2008, and published in the English language as PCTPublication No. WO 2008/145662, which application and publicationthereof are incorporated by reference herein in their entirety. The CVHsensing element is a circular arrangement of vertical Hall elementsarranged over a common circular implant region in a substrate. The CVHsensing element can be used to sense a direction (and optionally astrength) of a magnetic field in a plane of the substrate.

Conventionally, all of the output signals from the plurality of verticalHall elements within the CVH sensing element are needed in order todetermine a direction of a magnetic field. Also conventionally, outputsignals from the vertical Hall elements of a CVH sensing element aregenerated sequentially, resulting in a substantial amount of timenecessary to generate all of the output signals from the CVH sensingelement. Thus, determination of the direction of the magnetic field cantake a substantial amount of time.

Various parameters characterize the performance of magnetic fieldsensing elements. These parameters include sensitivity, which is achange in an output signal of a magnetic field sensing element inresponse to a change of magnetic field experienced by the magneticsensing element, and linearity, which is a degree to which the outputsignal of the magnetic field sensing element varies in direct proportionto the magnetic field. These parameters also include an offset, which ischaracterized by an output signal from the magnetic field sensingelement not representative of a zero magnetic field when the magneticfield sensing element experiences a zero magnetic field.

Another parameter that can characterize the performance of a CVH sensingelement is the speed with which output signals from vertical Hallelements within the CVH sensing element can be sampled, and thus, thespeed with which a direction of a magnetic field can be identified. Yetanother parameter that can characterize the performance of a CVH sensingelement is the resolution (e.g., angular step size) of the direction ofthe magnetic field that can be reported by the CVH sensing element.

As described above, the CVH sensing element is operable, with associatedcircuits, to provide an output signal representative of an angle of adirection of a magnetic field. Therefore, as described below, if amagnet is disposed upon or otherwise coupled to a so-called “targetobject,” for example, a camshaft in an engine, the CVH sensing elementcan be used to provide an output signal representative of an angle ofrotation, and/or a rotation speed, of the target object.

For reasons described above, a magnetic field sensor that uses a CVHsensing element may have a limit as to how rapidly the magnetic fieldsensor can identify the direction of a magnetic field, i.e., a rotationangle or rotation speed of a target object. Furthermore, the magneticfield sensor may provide an angular resolution that is too low (toolarge an angle step size). In general, it may be possible to provide ahigher resolution, but at the expense of more time.

Thus, it would be desirable to provide a magnetic field sensor that usesa CVH sensing element (or, more generally, a plurality of magnetic fieldsensing elements) and that can provide an improved output signal with ahigher angular (or positional) resolution while taking no additionaltime to provide the improved signal.

SUMMARY OF THE INVENTION

The present invention provides a magnetic field sensor that uses a CVHsensing element (or, more generally, a plurality of magnetic fieldsensing elements) and that can provide an improved output signal with ahigher angular (or positional) resolution while taking no additionaltime to provide the improved signal.

In accordance with one aspect of the present invention, a magnetic fieldsensor includes a semiconductor substrate having a first surface in anx-y plane. The magnetic field sensor also includes a CVH sensing elementcomprised of a plurality of vertical Hall elements. Each one of theplurality of vertical Hall elements is arranged upon a common circularimplant region in the first surface of the semiconductor substrate. Theplurality of vertical Hall elements is configured to generate aplurality of x-y output signals responsive to a magnetic field having adirection component parallel to the x-y plane. The CVH sensing elementis configured to generate a CVH output signal comprised of the pluralityof x-y output signals. The magnetic field results from a multi-polemagnet having a plurality of north poles and a plurality of south poles,each disposed in a plane parallel to the x-y plane, each north poleproximate to at least one south pole.

In accordance with another aspect of the present invention, a method ofposition sensing includes generating, with a CVH sensing element, aplurality of x-y output signals responsive to a magnetic field having adirection component in an x-y plane. The CVH sensing element iscomprised of a plurality of vertical Hall elements disposed in the x-yplane. The magnetic field result from a multi-pole magnet having aplurality of north poles and a plurality of south poles, each disposedin a plane parallel to the x-y plane, and each north pole proximate toat least one south pole. The method also includes generating a CVHoutput signal comprised of the plurality of x-y output signals.

In accordance with another aspect of the invention, a magnetic fieldsensor includes a CVH sensing element comprised of a plurality ofvertical Hall elements. Each one of the plurality of vertical Hallelements is arranged upon a common circular implant region in the firstsurface of the semiconductor substrate. The plurality of vertical Hallelements is configured to generate a plurality of x-y output signalsresponsive to a magnetic field having a direction component parallel tothe x-y plane. The CVH sensing element is configured to generate a CVHoutput signal comprised of the plurality of x-y output signals. Themagnetic field sensor also includes a clock generator configured togenerate a first clock signal and a second clock signal. The magneticfield sensor also includes an angle sensing circuit coupled to receivethe CVH output signal and configured to generate an x-y angle signalrepresentative of an angle of the direction component of the magneticfield. The angle sensing circuit includes a multiplexer coupled toreceive the CVH output signal at a first input and coupled to receivethe first clock signal at a second input. The multiplexer is configuredto generate a first multiplexed output signal comprised of the CVHoutput signal at some times and comprised of the first clock signal atother times. The angle sensing circuit further includes a comparatorcoupled to receive a signal representative of the first multiplexedoutput signal and configured to generate a comparison signal. Thecomparison signal has state transitions representative of zero crossingsof the CVH output signal at some times and state transitionsrepresentative of state transitions of the first clock signal at othertimes. The angle sensing circuit further includes a counter coupled toreceive the comparison signal, coupled to receive a signalrepresentative of the first clock signal, and coupled to receive asignal representative of the second clock signal. The counter isconfigured to generate a second multiplexed output signal comprised of afirst count signal at some times and comprised of a second count signalat other times. The angle sensing circuit further includes a combiningmodule coupled to receive a signal representative of the secondmultiplexed output signal and configured to generate the x-y anglesignal as a difference between the first count signal and the secondcount signal.

In accordance with another aspect of the invention, a method of positionsensing includes generating, with a CVH sensing element, a plurality ofx-y output signals responsive to a magnetic field having a directioncomponent parallel to the x-y plane. The CVH sensing element isconfigured to generate a CVH output signal comprised of the plurality ofx-y output signals. The method also includes generating a first clocksignal and a second clock signal. The method also includes generating anx-y angle signal representative of an angle of the direction componentof the magnetic field. The generating the x-y angle signal includesgenerating a first multiplexed output signal comprised of the CVH outputsignal at some times and comprised of the first clock signal at othertimes. The generating the x-y angle signal further includes generating acomparison signal from the first multiplexed output signal. Thecomparison signal has state transitions representative of zero crossingsof the CVH output signal at some times and state transitionsrepresentative of state transitions of the first clock signal at othertimes. The generating the x-y angle signal further includes generating asecond multiplexed output signal with a counter coupled to receive thecomparison signal, coupled to receive a signal representative of thefirst clock signal, and coupled to receive a signal representative ofthe second clock signal. The second multiplexed output signal iscomprised of a first count signal at some times and comprised of asecond count signal at other times. The generating the x-y angle signalfurther includes generating the x-y angle signal as a difference betweenthe first count signal and the second count signal.

With the above described magnetic field sensor and method, phasedifference that would result from two circuit channels are avoided,resulting in a more accurate magnetic field sensor and method.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention, as well as the invention itselfmay be more fully understood from the following detailed description ofthe drawings, in which:

FIG. 1 is a pictorial showing a two-pole ring magnet coupled to a targetobject and proximate to a substrate upon which a circular vertical Hall(CVH) sensing element and associated electronic circuits are disposed;

FIG. 2 is a pictorial showing a multi-pole ring magnet coupled to atarget object and proximate to a substrate upon which a circularvertical Hall (CVH) sensing element and associated electronic circuitsare disposed;

FIG. 3 is a block diagram of a CVH sensing element and an associatedelectronic circuit as may be used for the CVH sensing element andassociate electronic circuit of FIG. 2;

FIG. 4 is a graph showing a plurality of signals associated with the CVHsensing element and associate electronic circuits of FIG. 2;

FIG. 5 is a graph showing a another plurality of signals associated withthe CVH sensing element and associate electronic circuits of FIG. 2; and

FIG. 6 is a pictorial showing a multi-pole line magnet proximate to asubstrate upon which a circular vertical Hall (CVH) sensing element andassociated electronic circuits are disposed.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the present invention, some introductory concepts andterminology are explained. As used herein, the term “sensing element” isused to describe a variety of types of electronic elements that cansense a characteristic of the environment. For example, sensing elementsinclude, but are not limited to, pressure sensing elements, temperaturesensing elements, motion sensing elements, light sensing elements,acoustic sensing elements, and magnetic field sensing elements.

As used herein, the term “sensor” is used to describe a circuit orassembly that includes a sensing element and other components. Inparticular, as used herein, the term “magnetic field sensor” is used todescribe a circuit or assembly that includes a magnetic field sensingelement and electronics coupled to the magnetic field sensing element.

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing elements can be, but are not limitedto, Hall effect elements, magnetoresistance elements, ormagnetotransistors. As is known, there are different types of Halleffect elements, for example, a planar Hall element, a vertical Hallelement, and a circular Hall element. As is also known, there aredifferent types of magnetoresistance elements, for example, a giantmagnetoresistance (GMR) element, an anisotropic magnetoresistanceelement (AMR), a tunneling magnetoresistance (TMR) element, an Indiumantimonide (InSb) sensor, and a magnetic tunnel junction (MTJ).

As is known, some of the above-described magnetic field sensing elementstend to have an axis of maximum sensitivity parallel to a substrate thatsupports the magnetic field sensing element, and others of theabove-described magnetic field sensing elements tend to have an axis ofmaximum sensitivity perpendicular to a substrate that supports themagnetic field sensing element. In particular, planar Hall elements tendto have axes of sensitivity perpendicular to a substrate, whilemagnetoresistance elements and vertical Hall elements (includingcircular vertical Hall (CVH) sensing elements) tend to have axes ofsensitivity parallel to a substrate.

Magnetic field sensors are used in a variety of applications, including,but not limited to, an angle sensor that senses an angle of a directionof a magnetic field, a current sensor that senses a magnetic fieldgenerated by a current carried by a current-carrying conductor, amagnetic switch that senses the proximity of a ferromagnetic object, arotation detector that senses passing ferromagnetic articles, forexample, magnetic domains of a ring magnet, and a magnetic field sensorthat senses a magnetic field density of a magnetic field.

While a circular vertical Hall (CVH) magnetic field sensing element,which has a plurality of vertical Hall magnetic field sensing elements,is described in examples below, it should be appreciated that the sameor similar techniques and circuits apply to any type of sensing elementsand to any type of sensors, i.e., to any type of measuring devices. Inparticular similar circuits and techniques apply to a plurality ofseparate vertical Hall elements, not arranged in a CVH structure.

Referring to FIG. 1, an exemplary position sensing arrangement 10includes a two-pole ring magnet 12 having a north pole 12 a and a southpole 12 b. The ring magnet 12 is coupled to a shaft 14. The shaft 14 isa so-called “target object,” for which it is desired to sense a rotationor a rotational position.

A magnetic field sensor 15 includes a substrate 16 disposed proximate tothe ring magnet 12 and to the side of, e.g., in the same plane as, thering magnet 12.

A CVH sensing element and associated electronic circuit 18 are disposedupon the surface of the substrate 16. The substrate 16 together with theCVH sensing element and associated electronic circuit 18 form a magneticfield sensor 15 that can sense a position of the ring magnet 12. Themagnetic field sensor 15 is described more fully below in conjunctionwith FIG. 3.

It will be understood that the CVH sensing element and associateelectronic circuit 18 can provide an output signal representative of anangle of rotation of the ring magnet 12, and thus, an angle of rotationof the target object 14.

The magnetic field sensor 15 can generally provide an output signalrepresentative of the angle of rotation that has a range of values forevery complete rotation through three hundred sixty degrees of the ringmagnet 12 and the target object 14. It would be desirable to provide theoutput signal representative of the angle of rotation that has the samerange of values or a similar range of values upon a rotation of the ringmagnet 12 and the target object 14 through less than three hundred sixtydegrees. Such an arrangement can provide a more precise representationof the angle of rotation.

Referring now to FIG. 2, another exemplary position sensing arrangement30 includes a multi-pole ring magnet 32 having a plurality of northpoles and a plurality of south poles, of which a north pole 32 a and asouth pole 32 b are representative. The multi-pole ring magnet 32 iscoupled to a shaft 34, a target object 34. A substrate 36 is disposedproximate to the ring magnet 32 and to the side of, e.g., in the sameplane as, the multi-pole ring magnet 32.

A magnetic field sensor 35 includes a substrate 36 disposed proximate tothe ring magnet 32 and to the side of, e.g., in the same plane as, thering magnet 32.

A CVH sensing element and associated electronic circuit 38 are disposedupon a surface of a substrate 36. The substrate 36 together with the CVHsensing element and associated electronic circuit 38 form a magneticfield sensor 35 that can sense a position of the ring magnet 32. Themagnetic field sensor 35 is described more fully below in conjunctionwith FIG. 3.

It will be understood that the CVH sensing element and associatedelectronic circuit 38 can provide an output signal representative of anangle of rotation of the multi-pole ring magnet 32, and thus, an angleof rotation of the target object 34.

For reasons described more fully below, the magnetic field sensor 35 cangenerally provide an output signal having a range of valuesrepresentative of the angle of rotation of the ring magnet 32 and thetarget object 34 through less than three hundred sixty degrees, comparedto the magnetic field sensor 15 of FIG. 1. Thus, the magnetic fieldsensor 35 can provide a more precise representation of the angle ofrotation.

Referring now to FIG. 3, a magnetic field sensor 50 is responsive to amulti-pole ring magnet 51 upon a target object 53. The multi-pole ringmagnet 51 can be the same as or similar to the multi-pole ring magnet 32of FIG. 2. The magnetic field sensor 50 can be the same as or similar tothe magnetic field sensor 35 of FIG. 2 and can be disposed at the samerelative position relative to the ring magnet 51.

The magnetic field sensor 50 includes a CVH sensing element 52 comprisedof a plurality of vertical Hall elements. Each one of the plurality ofvertical Hall elements is arranged upon a common circular implant regionin a surface of a semiconductor substrate (not shown). The substrate canalso have all of the magnetic field sensor 50 disposed thereon. Theplurality of vertical Hall elements is configured to generate arespective plurality of x-y output signals responsive to a magneticfield having a time-varying direction component parallel to the x-yplane. In some embodiments, the magnetic field can have a time-varyingdirection in the x-y plane.

The CVH sensing element 52 is configured to generate a CVH output signal52 a comprised of the plurality of x-y output signals. The magneticfield results from the multi-pole magnet 51 having a plurality of northpoles and a plurality of south poles, each disposed in a plane parallelto the x-y plane, each north pole proximate to at least one south pole.In some embodiments, the multi-pole magnet 51 is configured to rotatewith a target object 53.

CVH sensing elements are known. CVH sensing element structure andfunction are described for example in PCT Patent Application No.PCT/EP2008/056517, entitled “Magnetic Field Sensor for MeasuringDirection of a Magnetic Field in a Plane,” filed May 28, 2008, andpublished in the English language as PCT Publication No, WO 2008/145662,which application and publication thereof are incorporated by referenceherein in their entirety.

Let it suffice here to say that the CVH sensing element 52 has aplurality of vertical Hall element contacts, for example, sixty-fourcontacts. Groups of the plurality of vertical Hall element contacts, forexample, groups of five vertical Hall element contacts, are eachrepresentative of one vertical Hall element within the CVH sensingelement. A vertical Hall element within the CVH sensing element 52 canshare some vertical Hall element contacts, for example, four verticalHall element contacts, with an adjacent vertical Hall element, i.e.,adjacent vertical Hall elements can overlap by four contacts.

Chopping is a known technique by which, at some times, selected ones ofthe vertical Hall element contacts within a vertical Hall element can bedriven by current sources 54 and a signal can be generated at otherselected ones of the vertical Hall element contacts within the verticalHall element. At other times, other selected ones of the vertical Hallelement contacts within the vertical Hall element can be driven by thecurrent sources 54 and another signal can be generated at still otherselected ones of the vertical Hall element contacts within the verticalHall element. For example, there can be four such chopped arrangementsof a given vertical Hall element within a chopping cycle. Thereafter,another vertical Hall element can be selected and the four choppingarrangements can again be performed, and so on.

Chopping is an optional arrangement herein. Thus, the CVH output signal52 a can have samples that are chopped or samples that are not chopped.

The magnetic field sensor 50 can include a switching circuit 56 thatprovides the sequencing among vertical Hall elements within the CVHsensing element 52 either without chopping or with chopping. Theswitching circuit 56 can be controlled by an oscillator with switcheslogic 58 by way of a clock (control) signal 58 a.

The current sources 54 can provide current signals 54 a to drive thevertical Hall elements within the CVH sensing element 52 sequentially orin parallel, and with or without chopping.

The oscillator and switches logic 58 can also generate a clock signal 58b that has a cycle frequency the same as a cycle frequency of the CVHoutput signal 52 a. The cycle frequency of the CVH output signal 52 a(and of the clock signal 58 b) has a period corresponding to onesequential cycle of vertical Hall element samples around the CVH sensingelement 52.

A circuit section 90 (also referred to herein as an angle sensingcircuit 90) can include a multiplexer 62, which can be an analogmultiplexer, which is coupled to receive the CVH output signal 52 a andcoupled to receive the clock signal 58 b. It should be apparent that theCVH output signal 52 a is an analog signal comprised of sequentialanalog samples, each sample from one of the vertical Hall elementswithin the CVH sensing element 52. It should also be apparent that theclock signal 58 b is a two state digital signal. The multiplexer 62 isconfigured to generate an output signal 62 a as a selected one of theCVH output signal 52 a or the clock signal 58 b at different respectivetimes.

The angle sensing circuit 90 can also include a differential differenceamplifier (DDA) coupled to receive the output signal 62 a from themultiplexer 62 and configured to generate an amplified signal 64 a.

The angle sensing circuit 90 can also include a bandpass filter 66coupled to receive the amplified signal 64 a and configured to generatea filtered signal 66 a.

The angle sensing circuit 90 can also include a comparator 68 coupled toreceive the filtered signal 66 a and configured to generate a comparisonsignal 68 a. The comparator 68 is also coupled to receive a thresholdvoltage (not shown).

The angle sensing circuit 90 can also include a counter 70 coupled toreceive the comparison signal 68 a, for example, at an enable input, andconfigured to generate a count signal 70 a.

The counter 70 is also coupled to receive a clock signal, for examplethe clock signal 58 b, for example, at a reset input, and to receive ahigher frequency clock signal, for example, the clock signal 58 a, at aclock input.

The angle sensing circuit 90 can also include a latch 71 coupled toreceive the count signal 70 a and configured to generate a latchedsignal 71 a.

The angle sensing circuit 90 can also include a combining module 72coupled to receive the latched signal 71 a.

The latch 71 is also coupled to receive the clock signal 58 b at a latchinput. More particularly, the clock signal 58 b received by the latch 71is slightly delayed from the clock signal 58 b received by the counter70.

In operation, the angle sensing circuit 90 separately processes, atdifferent times, the CVH sensing element signal 52 a and the clocksignal 58 b. Thus, at some times, the CVH output signal 52 a isamplified by the DDA 64, filtered by the bandpass filter 66, compared bythe comparator 68, counted by the counter 70, and latched by the latch71 to achieve a first count value. At other times, the clock signal 58 bis amplified by the DDA 64, filtered by the bandpass filter 66, comparedby the comparator 68, counted by the counter 70, and latched by thelatch 71 to achieve a second count value.

In this way, at some times, i.e., in some signal portions, the latchedsignal 71 a is representative of a first phase difference taken betweenthe CVH output signal 52 a (after experiencing a phase shift passingthough the circuit portion 90) and the clock signal 58 b as received bythe counter 70. At other times, i.e., in other signal portions, thelatched signal 71 a is representative of a second phase difference takenbetween the clock signal 58 b (after experiencing a phase shift passingthough the circuit portion 90) and the clock signal 58 b as received bythe counter.

The comparison module 72 is configured to generate a difference betweenthe first and second phase differences to generate a so-called “x-yangle signal” 72 a, which is representative of a direction of a magneticfield experienced by the CVH sensing element 52 in a plane (i.e., an x-yplane) of the CVH sensing element 52. In general, the plane of the CVHsensing element 52 is a major surface of the substrate on which the CVHsensing element 52 is disposed.

By using a common circuit channel, the angle sensing circuit 90eliminates phase differences between processing channels that would bepresent using two separate channels, one for the CVH sensing elementsignals 52 a and another for the clock signal 58 b. The phasedifferences would translate directly into an angle error in the magneticfield sensor 50, i.e., in the x-y angle signal 72 a. Thus, it will beunderstood that a difference between the first and second phasedifferences is representative of a phase difference between the CVHoutput signal 52 a and the clock signal 58 b, without phase errorsintroduced by the angle sensing circuit 90.

Referring again briefly to FIG. 1, it will be understood that, with thering magnet 12, the direction of the magnetic field experienced by theCVH sensing element and associated electronics 18 rotates through threehundred sixty degrees with every three hundred sixty degree revolutionof the ring magnet 12 and of the target object 14.

Referring again briefly to FIG. 2, it will be understood that, with themulti-pole ring magnet 32, the direction of the magnetic fieldexperienced by the CVH sensing element and associated electronics 38rotates several times through three hundred sixty degrees with every oneof the three hundred sixty degree revolutions of the multi-pole ringmagnet 32 and of the target object 34.

Referring again to FIG. 3, the magnetic field sensor 50 can include acorrection module 73 coupled to receive the x-y angle signal 72 a andconfigured to generate a corrected x-y angle signal 73 a. The correctionapplied by the correction module 73 can be, for example, a certainnumber of degrees, representative of, for example, an error in themounting angle of the magnetic field sensor 50 relative to the targetobject.

In some embodiments, one or more correction values can be supplied tothe correction module 73, for example, by a user. The one or morecorrection values can be stored within the correction module 73. In someembodiments, the correction module includes a non-volatile memory (notshown) to store the one or more correction values. Thus, a user cancorrect (e.g., rotate an indicated angle of) the x-y angle signal 72 ato provide a corrected x-y angle signal 73 a, corrected in accordancewith a mounting angle of the magnetic field sensor 50 relative to a zeroangle reference position of the ring magnet 51. It should be appreciatedthat the applied correction can be small, e.g., one degree, or can belarge, e.g., forty-five degrees.

In some other embodiments, there is no correction module 73.

The magnetic field sensor 50 can also include a pole pair countingmodule 74 coupled to receive the corrected x-y angle signal 73 a (or thex-y angle signal 72 a) and configured to generate a pole pair countsignal 74 a corresponding to a count of the number of pole pairs of thering magnet 51 that pass by the CVH sensing element 52. The pole paircounting module 74 can be configured to count up to some maximum value,for example, four, then reset to zero and start counting again. In someembodiments, the pole pair counting module 74 is also coupled to receiveanother position signal 86 a described more fully below.

The magnetic field sensor 50 can also include an angle interpolationmodule 76 coupled to receive the corrected x-y angle signal 73 a andcoupled to receive the pole pair count signal 74 a. Using the tworeceived signals, the angle interpolation module 76 is configured togenerate a position signal 76 a representative of a position, i.e., anangular position, of a target object, for example, the target object 53.However, the magnetic field experienced by the CVH sensing element 52goes through several revolutions for each one of the revolutions of thetarget object 34. The pole pair count signal 74 a is used by the angleinterpolation module 76 to identify which one of the revolutions of themagnetic field experienced by the CVH sensing element is applicable.

The magnetic field sensor 50 can also include an output protocol module82 coupled to receive the position signal 76 a and configured togenerate an output signal 82 a in one of a variety of standard formats.For example, the output signal 82 a can be in a SENT format, a VDAformat, a pulse width modulate (PWM) format, an I2C format, or anyserial or parallel format.

The magnetic field sensor 50 can also include a rotation speed module 78coupled to receive the position signal 76 a and configured to generate arotation speed signal 78 a representative of a rotation speed of thetarget object 53.

The magnetic field sensor 50 can also include a rotation directionmodule 80 coupled to receive the position signal 76 a and configured togenerate a rotation direction signal 80 a representative of a directionof rotation of the target object 53.

The output protocol module 82 can also be coupled to receive therotation speed signal 78 a and/or the rotation direction signal 80 a.The output protocol module 82 can be configured to combine one or bothof the rotation speed signal 78 a or the rotation direction signal 80 awith the position signal 76 a, all within the output signal 82 a.

The magnetic field sensor can also include a startup circuit 88 coupledto receive the position signal 76 a. The startup circuit can also beconfigured to receive another position signal 86 a from another positionsensor 86. The other position sensor can be responsive to a ring magnet84, e.g., a two-pole ring magnet 84, disposed on the same target object53, shown here separately for clarity. The ring magnet 84 can be thesame as or similar to the ring magnet 12 of FIG. 1.

The other position sensor 86 can be any type of position sensor. In someembodiments, the other position sensor 86 is like the magnetic fieldsensor 50, but without one or more of the modules 73, 74, 76, 78, 80,82. Thus, the other position sensor 86 can be configured to generate theother position signal 86 a to be like the x-y angle signal 72 a.

In some embodiments, the ring magnet 84 and the ring magnet 51 arejoined, for example, axially aligned and joined upon the same targetobject 53. In some embodiments, the other position sensor 86 can includeanother CVH sensing element like the CVH sensing element 52, and can befabricated upon the same substrate within the magnetic field sensor 50,along with other circuits like the circuits 54, 56, 58, and 90, with orwithout another correction module 73, all coupled to the other CVHsensing element. However, in other embodiments, the other positionsensor is fabricated upon a different substrate and within a differentintegrated circuit package than the magnetic field sensor 50.

The startup circuit 88 is configured to generate a signal 88 a as aselected one of the position signal 76 a or the other position signal 86a. In operation, the startup up circuit 88 can provide the otherposition signal 86 a as the signal 88 a to be embedded in the outputsignal 82 a for a time period beginning at startup of the magnetic fieldsensor 50 and the other position sensor 86 (or alternatively, a startupof rotation of the target object 53). Thereafter, the startup up circuit88 can provide the position signal 76 a as the signal 88 a to beembedded in the output signal 82 a. In embodiments that include thestartup circuit 88, the signal 76 a need not be coupled to the outputprotocol module 82.

It will be understood from discussion below in conjunction with FIGS. 4and 5 that the position signal 86 a can have a first resolution (numberof digital bits) and the position signal 76 a can have a seconddifferent resolution (number of digital bits) higher than the firstresolution. Thus, in some embodiments, the magnetic field sensor 50 canprovide the output signal 82 a with the first lower resolution for atime period following startup of the magnetic field sensor 50, and canthereafter provide the output signal 82 a with the second higherresolution.

In still other embodiments, the startup circuit 88 is not used and boththe position signal 76 a and the other position signal 86 a are bothreceived by the output protocol circuit 82 and both are always embeddedwithin the output signal 82 a. In these embodiments, the magnetic fieldsensor 50 can provide the output signal 82 with content having bothresolutions at the same time.

The rotation speed module 78 and the rotation direction module 80 arenot described further herein. Circuits and techniques that can achievethe rotation speed module 78 and the rotation direction module 80 aredescribed in U.S. patent application Ser. No. 13/084,745, filed Apr. 12,2011, and entitled “A Magnetic Field Sensor That Provides An OutputSignal Representative Of An Angle Of Rotation And A Speed Of Rotation OfThe Target Object,” which application is Incorporated by referenceherein in its entirety, and which application is assigned to theassignee of the present invention. Other techniques to achieve therotation speed module 78 and the rotation direction module 80 arepossible.

Referring now to FIG. 4, a graph 100 includes a horizontal axis with ascale in units of a rotational angle of the target object 53 of FIG. 3.The graph 100 also includes a vertical axis with several scales inarbitrary units and identified by text to the right of the graph 100.

North and south poles 102 are representative of north and south poles ofthe multi-pole ring magnet 51 of FIG. 3 relative to angular position ofthe ring magnet 51, i.e., as they pass by the magnetic field sensor 50of FIG. 3. It will be understood that all of the plurality of north andsouth poles rotate past the magnetic field sensor 50 of FIG. 3 upon onerotation through three hundred and sixty degrees of the target object,e.g., 51 of FIG. 3. Thus, the magnetic field sensor 50 and the CVHsensing element 52 disposed thereon experience a magnetic field thatrotates more rapidly than the target object 53.

A signal 104 is representative of a magnetic field experienced by theCVH sensing element 52 of FIG. 3 as the multi-pole ring magnet 53represented by the north and south poles of FIG. 4 rotates through threehundred sixty degrees.

A signal 106 is representative of the x-y angle signal 72 a of FIG. 3.As described above, the x-y angle signal 72 a is a multi-bit digitalsignal. The signal 106 is an analog representation of the x-y anglesignal 72 a. It will be appreciated that the signal 106 can also berepresentative of the corrected x-y angle signal 73 a of FIG. 3.

The signal 106 has a plurality of cycles 106 a-106 d corresponding tothe plurality of cycles of the signal 104. The signal 106 isrepresentative of the rotation angle, i.e., angular position, of thetarget object 53 of FIG. 3, however, with ambiguity. Each one of thecycles 106 a-106 d of the signal 106 can be representative of a fullrange of values indicative of zero to three hundred sixty degreesrotation of a sensed magnetic field.

The signal 106 can have a first number of digital bits indicative of afirst angular resolution. It will be appreciated that the first angularresolution applies to a magnetic field rotation through three hundredsixty degrees, and thus, the first angular resolution is the same asthat which would be achieved by the arrangement of FIG. 1, and also bythe other position sensor 86 of FIG. 3 responsive to one pole pair ofthe ring magnet 84.

A signal 108 is representative of the pole pair count signal 74 a ofFIG. 3. As described above, the pole pair count signal 74 a is amulti-bit digital signal. The signal 108 is an analog representation ofthe pole pair count signal 74 a.

The signal 108 has a plurality of steps 108 a-108 d, i.e. changes ofvalue, corresponding to counts of the plurality of cycles of the signal104.

A signal 110 is representative of the position signal 76 a of FIG. 3. Aswill be understood, the angle interpolation module 76 can identify whichone of the pole pairs counted by the signal 108 is associated with whichone of the cycles of the signal 106. Essentially, with this information,the angle interpolation module 76 can reconstruct the signal 106 intothe signal 110, removing the angular position ambiguity of the signal106.

The signal 110 can have a second number of digital bits, which canprovide a higher resolution than the first resolution provided by thefirst number of bits of the signal 106. In the exemplary arrangementrepresented by the graph 100, in which the signal 106 has four cycles,the second resolution of the signal 110 can be four times the firstresolution of the signal 106, i.e., the signal 110 can have two moredigital bits than the signal 106.

Referring now to FIG. 5, a graph 120 includes a horizontal axis with ascale in units of a rotational angle of the target object 34 of FIG. 2.The graph 120 also includes a vertical axis with several scales inarbitrary units and identified by text to the right of the graph 100.

North and south poles 124 are representative of north and south poles ofthe multi-pole ring magnet 51 of FIG. 3 relative to angular position ofthe ring magnet 32, i.e., as they pass by the CVH sensing element 52 ofFIG. 3. It will be understood that all of the plurality of north andsouth poles rotate past the CVH sensing element 52 of FIG. 3 upon onerotation through three hundred and sixty degrees of the target object 53of FIG. 3.

A north and south pole 122 are representative of the north and southpoles of the two pole ring magnet 84 of FIG. 3, to which the otherposition sensor 86 of FIG. 3 is responsive.

A signal 128 is comparable to the signal 104 of FIG. 4. A signal 130,having a plurality of cycles 130 a-130 d, is comparable to the signal106 of FIG. 4. A signal 132, having a plurality of cycles 108 a-108 d,is comparable to the signal 108 of FIG. 4. A signal 134 is comparable tothe signal 110 of FIG. 4.

A signal 126 is representative of a magnetic field experienced by theother magnetic field sensor 86 of FIG. 3, which is responsive to thenorth and south poles of the ring magnet 84, like the north and southpoles 122.

The other magnetic field sensor 86 of FIG. 3 generates the otherposition signal 86 a of FIG. 3 like one of the cycles of the signal 130of FIG. 5, but extending in but one cycle from zero to three hundredsixty degrees rotation of the target object 53 of FIG. 3. This signal isnot shown in the graph 120, but will be readily understood.

The signal 134 (i.e., the position signal 76 a of FIG. 3) achieves thehigher second resolution, higher than the resolution of the otherposition signal 86 a.

Referring now to FIG. 6, another exemplary position sensing arrangement150 includes a multi-pole line magnet 152 having a plurality of northand south poles, of which a north pole 152 a and a south pole 152 b arerepresentative. The line magnet 152 is coupled to a target object (notshown) for which it is desired to sense a movement or a linear position.

The multi-pole line magnet 152 and the target object can be arranged tomove in a direction 158, or in the opposite direction.

A magnetic field sensor 153 includes a substrate 154 disposed proximateto the multi-pole line magnet 152 in the same plane as magnetic fieldlines that exist between the north and south poles.

A CVH sensing element and associated electronic circuit 156 are disposedupon a surface of a substrate 154. The magnetic field sensor 153 can bethe same as or similar to the magnetic field sensor 50 of FIG. 3.

It will be understood that the magnetic field sensor 153 can provide anoutput signal representative of a linear position of the multi-pole linemagnet 152, and thus, a linear position of the target object (not shown)to which the multi-pole line magnet is coupled.

Operation of the magnetic field sensor will be understood from thediscussion above in conjunction with FIGS. 3 and 4.

As with arrangements are described above, it should be appreciated thatthe magnetic field sensor 153 identifies the position of the targetobject (not shown) with a higher resolution than that provided byconventional techniques used with a CVH sensing element.

All references cited herein are hereby incorporated herein by referencein their entirety.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent to those of ordinary skill inthe art that other embodiments incorporating these concepts, structuresand techniques may be used. Accordingly, it is submitted that that scopeof the patent should not be limited to the described embodiments butrather should be limited only by the spirit and scope of the followingclaims.

What is claimed is:
 1. A magnetic field sensor, comprising: a semiconductor substrate having a first surface in an x-y plane; a Circular Vertical Hall (CVH) sensing element comprised of a plurality of vertical Hall elements, wherein each one of the plurality of vertical Hall elements is arranged upon a common circular implant region in the first surface of the semiconductor substrate, wherein the plurality of vertical Hall elements is configured to generate a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to the x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals, wherein the magnetic field results from a multi-pole magnet having a plurality of north poles and a plurality of south poles, each disposed in a plane parallel to the x-y plane, each north pole proximate to at least one south pole; an angle sensing circuit coupled to receive the CVH output signal and configured to generate an x-y angle signal representative of an angle of the direction component of the magnetic field as the multi-pole magnet and the CVH sensing element move relative to each other; a pole pair counting module coupled to receive a signal representative of the x-y angle signal and configured to generate a count signal representative of a count of a number of the pole pairs of the multi-pole magnet that move past the CVH sensing element; and an angle interpolation module coupled to receive the x-y angle signal and the count signal, the angle interpolation module configured to generate a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
 2. The magnetic field sensor of claim 1, wherein the multi-pole magnet comprises a multi-pole ring magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
 3. The magnetic field sensor of claim 2, wherein the ring magnet is movably disposed to rotate about an axis perpendicular to the x-y plane.
 4. The magnetic field sensor of claim 1, wherein the multi-pole magnet comprises a multi-pole line magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
 5. The magnetic field sensor of claim 4, wherein the line magnet is movably disposed to move along a line in the x-y plane.
 6. The magnetic field sensor of claim 4, wherein the CVH sensing element is movably disposed to move along a line in the x-y plane.
 7. The magnetic field sensor of claim 1, wherein the interpolated signal provides a first resolution of the position of the multi-pole magnet relative to the CVH sensing element, wherein the magnetic field sensor further comprises: a magnetic field sensing element configured to generate a magnetic field sensing element output signal responsive to a magnetic field generated by a second multi-pole magnet having at least one north pole and at least one south pole; an electronic circuit coupled to receive the magnetic field sensing element output signal and configured to generate a position signal, wherein the position signal is representative of the position of the second multi-pole magnet relative to the magnetic field sensing element with a second different resolution; and an output protocol module coupled to receive the interpolated signal and the position signal, and configured to generate an output signal representative of the position signal at some times and configured to generate the output signal representative of the interpolated signal at other times.
 8. A method of position sensing, comprising: generating, with a Circular Vertical Hall (CVH) sensing element, a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals, wherein the magnetic field result from a multi-pole magnet having a plurality of north poles and a plurality of south poles, each disposed in a plane parallel to the x-y plane, each north pole proximate to at least one south pole; generating a CVH output signal comprised of the plurality of x-y output signals; generating an x-y angle signal representative of an angle of the direction component of the magnetic field as the multi-pole magnet and the CVH sensing element move relative to each other; generating a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that moves past the CVH sensing element; and generating a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
 9. The method of claim 8, wherein the multi-pole magnet comprises a multi-pole ring magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
 10. The method of claim 9, wherein the ring magnet is movably disposed to rotate about an axis perpendicular to the x-y plane.
 11. The method of claim 8, wherein the multi-pole magnet comprises a multi-pole line magnet, and wherein the plurality of north poles and a plurality of south poles are disposed in the x-y plane.
 12. The method of claim 11, wherein the line magnet is movably disposed to move along a line in the x-y plane.
 13. The method of claim 11, wherein the CVH sensing element is movably disposed to move along a line in the x-y plane.
 14. The method claim 8, wherein the interpolated signal provides a first resolution of the position of the multi-pole magnet relative to the CVH sensing element, wherein the method further comprises: generating a magnetic field sensing element output signal responsive to a magnetic field generated by a second multi-pole magnet having at least one north pole and at least one south pole; generating a position signal is representative of the position of the second multi-pole magnet relative to the magnetic field sensing element with a second different resolution; and generating an output signal representative of the position signal at some times and generating the output signal representative of the interpolated signal at other times.
 15. A magnetic field sensor, comprising: a Circular Vertical Hall (CVH) sensing element comprised of a plurality of vertical Hall elements, wherein each one of the plurality of vertical Hall elements is arranged upon a common circular implant region in a first surface of a semiconductor substrate, wherein the plurality of vertical Hall elements is configured to generate a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals; a clock generator configured to generate a first clock signal and a second clock signal; an angle sensing circuit coupled to receive the CVH output signal and configured to generate an x-y angle signal representative of an angle of the direction component of the magnetic field, wherein the angle sensing circuit comprises: a multiplexer coupled to receive the CVH output signal at a first input and coupled to receive the first clock signal at a second input and configured to generate a first multiplexed output signal comprised of the CVH output signal at some times and comprised of the first clock signal at other times; a comparator coupled to receive a signal representative of the first multiplexed output signal and configured to generate a comparison signal, wherein the comparison signal has state transitions representative of zero crossings of the CVH output signal at some times and state transitions representative of state transitions of the first clock signal at other times; a counter coupled to receive the comparison signal, coupled to receive a signal representative of the first clock signal, and coupled to receive a signal representative of the second clock signal, wherein the counter is configured to generate a second multiplexed output signal comprised of a first count signal at some times and comprised of a second count signal at other times; and a combining module coupled to receive a signal representative of the second multiplexed output signal and configured to generate the x-y angle signal as a difference between the first count signal and the second count signal; a pole pair counting module coupled to receive the x-y angle signal and configured to generate a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that move past the CVH sensing element; and an angle interpolation module coupled to receive the x-y angle signal and the pole pair count signal, the angle interpolation module configured to generate a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
 16. A method of position sensing, comprising: generating, with a Circular Vertical Hall (CVH) sensing element, a plurality of x-y output signals responsive to a magnetic field having a direction component parallel to an x-y plane, wherein the CVH sensing element is configured to generate a CVH output signal comprised of the plurality of x-y output signals; generating a first clock signal and a second clock signal; and generating an x-y angle signal representative of an angle of the direction component of the magnetic field, wherein the generating the x-y angle signal comprises: generating a first multiplexed output signal comprised of the CVH output signal at some times and comprised of the first clock signal at other times; generating a comparison signal from the first multiplexed output signal, wherein the comparison signal has state transitions representative of zero crossings of the CVH output signal at some times and state transitions representative of state transitions of the first clock signal at other times; generating a second multiplexed output signal with a counter coupled to receive the comparison signal, coupled to receive a signal representative of the first clock signal, and coupled to receive a signal representative of the second clock signal, wherein the second multiplexed output signal is comprised of a first count signal at some times and comprised of a second count signal at other times; and generating the x-y angle signal as a difference between the first count signal and the second count signal; generating a pole pair count signal representative of a count of a number of the pole pairs of the multi-pole magnet that moves past the CVH sensing element; and generating a reconstructed x-y angle signal representative of an angular position of the multi-pole magnet relative to the CVH sensing element, the reconstructed x-y angle signal generated based upon the pole pair count signal and the x-y angle signal, the reconstructed x-y angle signal having a higher resolution than the x-y angle signal.
 17. The magnetic field sensor of claim 1, wherein the reconstructed x-y angle signal removes an ambiguity from the x-y angle signal of the angular position of the multi-pole magnet relative to the CVH sensing element.
 18. The method of claim 8, wherein generating the reconstructed x-y angle signal comprises removing an ambiguity from the x-y angle signal of the angular position of the multi-pole magnet relative to the CVH sensing element. 